JP2014088863A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine provided with a combustion chamber having a heat shielding structure, in which a reduction in charging efficiency is suppressed to suppress deterioration in fuel consumption due to the reduction in charging efficiency.SOLUTION: An internal combustion engine 10 includes: a combustion chamber 16 defined by a cylinder bore 11 provided in a cylinder block 12, an apex portion of a piston 13, and a lower face of a cylinder head 15; and a heat shielding ring 23 disposed on an apex portion of the cylinder block 12 so as to be arranged adjacent to the cylinder bore 11 in an axial direction, for suppressing heat transfer to the cylinder block 12 from the inside of the combustion chamber 16.

Description

  The present invention relates to an internal combustion engine in which a combustion chamber having a heat shielding structure is formed.

  In internal combustion engines (engines), attempts have been made to improve fuel efficiency by reducing cooling loss. In such an internal combustion engine, for example, a cylinder liner made of a low thermal conductivity material is inserted into a cylinder bore of a cylinder block so that the combustion chamber has a heat shielding structure (see Patent Document 1).

JP 2005-330873 A

  However, since the above-described internal combustion engine uses a thick ceramic for the cylinder liner, the heat capacity of the combustion chamber is large, and the temperature in the combustion chamber (in-cylinder temperature) increases throughout the entire stroke. Therefore, there is a problem that the charging efficiency is lowered and the combustion is slowed down due to lack of oxygen, and as a result, the fuel efficiency may not be improved.

  In particular, the cylinder bore of the cylinder block is covered with a cylinder liner made of a thick ceramic from the upper end to the lower end of the overall height, and therefore contributes greatly to a decrease in filling efficiency. The reason is that fresh air or intake air having a low temperature entering the combustion chamber during the intake stroke (atmospheric temperature to about 50 ° C.) is heated to expand to about 100 to 200 ° C. by a cylinder bore (cylinder liner) of several hundred degrees. Because.

  Accordingly, an object of the present invention is to suppress deterioration in fuel consumption caused by a decrease in charging efficiency by suppressing a decrease in charging efficiency in an internal combustion engine in which a combustion chamber having a heat shielding structure is formed.

  In order to achieve the above object, an internal combustion engine according to the present invention includes a combustion chamber defined by a cylinder bore provided in a cylinder block, a top portion of a piston, and a lower surface of a cylinder head, and the top portion of the cylinder block. And a heat shield ring which is provided adjacent to the cylinder bore in the axial direction and suppresses heat transfer from the combustion chamber to the cylinder block.

  The heat shield ring may include a cylindrical heat shield ring main body and a heat shield layer formed on an inner peripheral surface of the heat shield ring main body.

  The heat shield layer is formed on the inner peripheral surface of the heat shield ring main body by applying a heat shield paint to the inner peripheral surface of the heat shield ring main body or applying porous plating to the inner peripheral surface of the heat shield ring main body. It may be a thermal barrier coating layer.

  According to the present invention, in an internal combustion engine in which a combustion chamber having a heat-shielding structure is formed, an excellent effect of suppressing deterioration in fuel efficiency due to a decrease in charging efficiency can be achieved by suppressing a decrease in charging efficiency. Play.

(A) is typical sectional drawing of the internal combustion engine which concerns on one Embodiment of this invention, (b) is the sectional view on the AA line of (a). It is a principal part enlarged view of Fig.1 (a).

  Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  As shown in FIG. 1, an internal combustion engine (in this embodiment, a diesel engine) 10 according to this embodiment includes a cylinder block 12 having a cylinder bore 11, a piston 13 that reciprocates up and down in the cylinder bore 11, and a cylinder block. And a cylinder head 15 attached to the top (upper part) of 12 with a cylinder head gasket 14 interposed therebetween. The cylinder block 12, the piston 13 and the cylinder head 15 are made of a metal material such as steel or an aluminum alloy.

  A space surrounded by the cylinder bore 11 provided in the cylinder block 12, the top of the piston 13, and the lower surface of the cylinder head 15 forms a combustion chamber 16. The cylinder block 12 is provided with a water jacket 17 so as to surround the cylinder bore 11. Further, a cavity (in the illustrated example, a cavity with a lip) 18 is provided at the top of the piston 13. Further, the cylinder head 15 includes an intake / exhaust port (intake port 19 and exhaust port 20) communicating with the combustion chamber 16, an intake valve 21 for opening and closing the intake port 19, an exhaust valve 22 for opening and closing the exhaust port 20, A fuel injection valve (not shown) for injecting fuel into the combustion chamber 16 from above is provided.

  In the internal combustion engine 10 according to the present embodiment, a heat shield ring 23 that suppresses heat transfer from the combustion chamber 16 to the cylinder block 12 is provided in the cylinder bore 11 at the top of the cylinder block 12 (near the top dead center TDC of the piston 13). On the other hand, the combustion chamber 16 has a heat shielding structure by being provided adjacent to the axial direction. In the internal combustion engine 10 according to the present embodiment, an accommodation bore 24 having a diameter larger than that of the cylinder bore 11 is provided on the top of the cylinder block 12 so as to be continuous in the axial direction with respect to the cylinder bore 11. 23 is press-fitted.

  The heat shield ring 23 includes a tubular or ring-shaped (cylindrical in the illustrated example) heat shield ring body 25 and a heat shield layer 26 formed on the inner peripheral surface of the heat shield ring body 25. The heat shield layer 26 is applied to the inner peripheral surface of the heat shield ring main body 25 by applying a heat shield paint to the inner peripheral surface of the heat shield ring main body 25 or by applying porous plating to the inner peripheral surface of the heat shield ring main body 25. It is a thin film thermal barrier coating layer to be formed. That is, the heat shield layer (heat shield coating layer) 26 formed on the inner peripheral surface of the heat shield ring 23 (heat shield ring body 25) has a thickness tm (see FIG. 2) of about 100 μm and has a heat shield paint. And a porous material (porous material). On the other hand, the heat shield ring body 25 is made of a metal material such as steel or an aluminum alloy.

  FIG. 2 shows an enlarged view of the main part of FIG.

  The height (ring width) h of the heat shield ring 23 is preferably relatively low, for example, about 10 mm. The reason why the height h of the heat shield ring 23 is made relatively low is to arrange the heat shield ring 23 while avoiding the sliding range of the piston 13. When the piston 13 is located at the top dead center TDC, the clearance CL of the heat shield ring 23 is set such that the distance CL between the upper end of the top ring 27 attached to the piston 13 and the lower end of the heat shield ring 23 is, for example, about 1 to 2 mm. Height h is set.

  Moreover, it is preferable to make the thickness t of the heat shield ring 23 relatively thin, for example, about 1-2 mm. The reason why the thickness t of the heat shield ring 23 is made relatively thin is to arrange the heat shield ring 23 while avoiding the sealing range of the cylinder head gasket 14.

  Further, the inner peripheral surface of the heat shield ring 23 is slightly recessed with respect to the cylinder bore 11, and the difference Δt between the inner diameter (after coating) φd of the heat shield ring 23 and the inner diameter φD of the cylinder bore 11 is about 0.1 mm, for example. It is said. That is, the inner diameter φd of the heat shield ring 23 is larger than the inner diameter φD of the cylinder bore 11 (φD <φd).

  Further, the top surface (upper surface) of the heat shield ring 23 is slightly recessed with respect to the top surface of the cylinder block 12, and the height difference Δh between the top surface of the heat shield ring 23 and the top surface of the cylinder block 12. Is, for example, about 0.1 mm.

  Next, the effect of the internal combustion engine 10 according to the present embodiment will be described.

  In the internal combustion engine 10 according to the present embodiment, a heat shield ring 23 that suppresses heat transfer from the combustion chamber 16 to the cylinder block 12 is provided in the cylinder bore 11 at the top of the cylinder block 12 (near the top dead center TDC of the piston 13). On the other hand, the combustion chamber 16 has a heat shielding structure by being provided adjacent to the axial direction. That is, in the internal combustion engine 10 according to the present embodiment, heat is not shielded from the upper end to the lower end of the overall height of the cylinder bore 11, but only the upper portion of the cylinder bore 11 having a great influence on the cooling loss is shielded by the heat shield ring 23. . By configuring the combustion chamber 16 in this way, the heat capacity of the combustion chamber 16 can be reduced, the reduction in charging efficiency is very small, and the deterioration of fuel consumption due to the reduction in charging efficiency does not occur. Therefore, fuel consumption can be improved by reducing the cooling loss.

  Furthermore, in the internal combustion engine 10 according to the present embodiment, in order to reduce the heat capacity of the combustion chamber 16, a thin thermal barrier layer (thermal barrier coating layer) 26 is formed on the inner peripheral surface of the thermal barrier ring 23 (thermal barrier ring body 25). Therefore, the decrease in charging efficiency is very small, and the fuel consumption caused by the decrease in charging efficiency does not occur. The reason why the heat capacity of the combustion chamber 16 is reduced is that it is not necessary to use a thick ceramic for the heat shield ring 23 (heat shield ring main body 25), and a metal material such as steel or aluminum alloy generally used for the internal combustion engine 10 is used. Because it can.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various other embodiments can be adopted.

  For example, the present invention can be applied not only to a diesel engine but also to a gasoline engine or the like.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11 Cylinder bore 12 Cylinder block 13 Piston 15 Cylinder head 23 Thermal insulation ring 25 Thermal insulation ring main body 26 Thermal insulation coating layer (thermal insulation layer)

Claims (3)

  In an internal combustion engine having a combustion chamber defined by a cylinder bore provided in a cylinder block, a top of a piston, and a lower surface of a cylinder head, the combustion is provided at the top of the cylinder block adjacent to the cylinder bore in the axial direction. An internal combustion engine comprising a heat shield ring that suppresses heat transfer from a room to the cylinder block.   2. The internal combustion engine according to claim 1, wherein the heat shield ring includes a cylindrical heat shield ring main body and a heat shield layer formed on an inner peripheral surface of the heat shield ring main body.   The heat shield layer is formed on the inner peripheral surface of the heat shield ring main body by applying a heat shield paint to the inner peripheral surface of the heat shield ring main body or applying porous plating to the inner peripheral surface of the heat shield ring main body. The internal combustion engine according to claim 2, which is a thermal barrier coating layer.

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